Minion wave management is a critical skill for high-level play. Freezing a lane involves keeping the minion wave just outside your tower's range, allowing you to safely farm and deny enemy gold/experience. This is great for setting up ganks. Slow pushing involves building up a large minion wave by only last-hitting, which then crashes into the enemy tower, creating pressure and allowing you to roam. Fast pushing involves quickly clearing a minion wave to reset the lane, recall, or rotate to another objective. Mastering these techniques gives you immense control over the lane and map tempo.

Advanced Wave Management: Freezing, Slow Pushing, Fast Pushing — League of Legends Guide